kvv2: handle data_json not being set on ignored lifecycle

[fairclothjm]

Description

Handle the scenario where ignore_changes is true for data_json after import

Closes #2205

Checklist

• [x] Added CHANGELOG entry (only for user-facing changes)
• [ ] Acceptance tests where run against all supported Vault Versions

[fairclothjm]

Superceded by https://github.com/hashicorp/terraform-provider-vault/pull/2207